The present invention relates to an information processing apparatus, and more specifically, to an information processing apparatus in which an information memory medium, such as an optical disk, is rotated so that information is recorded, reproduced, or erased by means of laser beams.
Recently, information processing apparatuses have started to be used frequently which employ an optical disk as a memory medium. As compared with those information processing apparatuses using conventional magnetic memory media, the apparatuses of this type have the following advantages. They have a larger information memory capacity, and can better perform extremely stable reproduction of information with less noise. Moreover, the improved apparatuses are less susceptible to external influences, thus enjoying very stable memory conditions. Also, they can perform information processing with the memory media not in contact with an information processing head, so that the media and head are less liable to be damaged.
As these information recording/reproducing apparatus have come into general use, the demand for thinner, lighter and less expensive apparatus have increased. However, the conventional apparatus cannot meet this demand for the following reason.
In order to hold the information memory medium or optical disk on a turntable, the disk is pressed against a turntable from the opposite side thereof, by means of a clamper. The clamper receives a clamping force from urging means, such as springs, or by magnetic attraction produced between the clamper and turntable. In the latter case, the clamper has a magnet, and the turntable is formed of magnetic material. The conventional apparatuses require a space for accommodating the clamper. Further, they need a drive mechanism for moving the clamper toward or away from the optical disk. As a result, the apparatus is bulky and complicated in construction, thus inevitably thick, heavy and expensive. Also, the use of the clamp mechanism makes it difficult to assemble the apparatus and to keep it in good condition.
If the clamp mechanism is of a spring type, the turntable is always subjected to an urging force. Therefore, the turntable, along with a rotating shaft integral therewith, must be made strong enough to resist the force. If the clamp mechanism is of a magnet type, the clamping force varies, depending on the thickness of the optical disk. When using relatively thick memory media, such as those including two bases stuck together, the clamping force may sometimes be reduced too much to hold the media securely.